It didn't do anything that a modern ATX case with a couple of 120mm fans couldn't do better.
That's nonsense.
BTX is clearly superior to ATX's non-existant solution to thermals and airflow (the basic idea being have a huge CPU cooler waft hot air around the entire case, with a smattering of large blowholes trying to evacuate it), especially when considering today's super-hot graphics cards, especially in SLI mode. One needed quite a few fans to beat the simple and elegant solution in BTX.
I don't get why people are so negative to BTX anyway, not when it is so obviously just plain BETTER. Simply the idea of switching the card slots around so hot electronics isn't facing downwards, inwards on itself is such a 'duh' moment one has to wonder why it took such a hell of a long time to carry out.
Add to that, the difficulties with jiggling in sufficient north and southbridge coolers when both are in close proximity to cardslots, DIMM levers interfering with the VGA card etc... One realizes ATX simply wasn't MADE for the condition that exists today. Yes, it can be juryrigged into working, and very rarely even working very well, but that isn't often seen. Extremely few ATX mobos don't have at least some kind of quirk or niggle that irritates or annoys. An oddly placed power connector, or a IDE ribbon cable that gets squeezed somehow, or the inability to fit that particular CPU cooler due to a capacitor that's too close or too tall.
ATX is old junk that needs to be tossed. No redeeming features about it whatsoever - other than simply being very prevalent, but so were the model-T fords once too. We don't drive around in cars like that anymore though, and for good reason. ATX needs to go defunct. It's POS.